1. Field of the Invention
The present invention relates generally to methods and arrangements for detecting and responding to faults in electrical power systems and more particularly to methods and arrangements that utilize directional sensing to determine whether or not a fault is internal or external to a particular circuit point.
2. Description of Related Art
Various methods and arrangements have been proposed and/or used to detect and respond to fault conditions in electrical power systems. For example, various instantaneous and time-current protective devices sense and respond to fault conditions either by directly interrupting the fault or by both interrupting and isolating the fault condition via communication/cooperation with one or more other devices. For example, see the following U.S. Pat. Nos. for examples of these types of systems: 6,018,449; 5,784,237; 5,303,112; 5,701,226; 5,341,268; 5,793,750. A specific type of fault detection is a bus differential protection arrangement that operates by summing individual phase currents and detecting a fault based on the algebraic sum exceeding a given threshold.
While the arrangements of the prior art may be useful and generally satisfactory for their intended purposes, they are not always capable of detecting and responding to fault conditions due to problems with communications or other misoperations.
Accordingly, it is a principal object of the present invention to provide arrangements and methods for detecting and responding to faults in electrical power systems to isolate the faults and provide continued desirable fault protection for the reconfigured system.
It is another object of the present invention to provide a method and arrangement to detect whether faults are external or internal to a distribution equipment configuration in a power system via directional sensing.
It is still another object of the present invention to provide a method and arrangement to detect and respond to faults in a power distribution system utilizing various combinations of primary and back-up protection arrangements that are operational simultaneously and in both closed-loop and open-loop configurations.
These and other objects of the present invention are efficiently achieved by arrangements and methods for detecting and responding to faults in electrical power distribution systems. The present invention provides methods and arrangements to detect whether faults are external or internal to a distribution equipment configuration in a power system via directional sensing. The present invention also detects and responds to faults in a power distribution system utilizing various combinations of primary and back-up protection arrangements that are operational simultaneously and in both closed-loop and open-loop configurations.